Display Device Pad Area Layer Segmentation for Short Prevention
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Solution Overview
Problem
Existing display devices face challenges in minimizing step coverage defects and preventing shorts in the pad area due to the complex arrangement of conductive layers, which affects the reliability and performance of the display.
Innovation Solution
A display device structure is designed with multiple conductive layers in the display area, where only specific layers are used in the pad area, incorporating a passivation layer and touch insulating layers made of inorganic and organic materials to minimize defects and ensure proper electrical connections, including a unique arrangement of pad electrodes and connection electrodes to prevent shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple conductive layers are arranged in the pad area to ensure proper electrical connections, then electrical connectivity is improved, but step coverage defects and shorts increase
Solution Approach 1:
The pad area structure is segmented into distinct functional layers: a first pad electrode in the first conductive layer, a second pad electrode in the second conductive layer, and a third pad electrode in the third conductive layer. Each layer serves specific electrical connection functions, allowing proper signal routing while maintaining manufacturing feasibility by avoiding excessive layer stacking in the pad region.
Solution Approach 2:
Different regions of the display device are assigned different structural qualities: the display area contains multiple conductive layers (first through fifth) for complex pixel electrode connections, while the pad area uses a simplified three-layer configuration (first through third conductive layers) optimized for electrical connections to external circuits. This local differentiation reduces step coverage defects in the pad area while maintaining functionality.
2Reliability
If multiple conductive layers are arranged in the pad area to ensure proper electrical connections, then electrical connectivity is improved, but the risk of shorts increases
Solution Approach 1:
An insulating layer is introduced as an intermediary between the third conductive layer (containing the third pad electrode) and the fourth conductive layer (containing connection electrodes). This insulating barrier prevents direct contact between conductive elements from different layers, eliminating short circuit risks while allowing vertical electrical connections through controlled vias and contact holes in the insulating layer.
Solution Approach 2:
The electrical connection path is segmented into discrete stages: the third pad electrode in the third conductive layer connects to external circuits, while connection electrodes in the fourth conductive layer connect to pixel electrodes through the insulating layer. This segmentation isolates different electrical functions into separate layers, preventing unintended electrical contact and shorts.
3Ease of manufacture
If all conductive layers are extended to the pad area, then manufacturing simplicity is improved, but step coverage defects increase
Solution Approach 1:
The conductive layer configuration is optimized locally for the pad area: only the first through third conductive layers are formed in the pad region, while the fourth and fifth conductive layers are restricted to the display area. This local differentiation reduces the number of stacked layers in the pad area, minimizing step coverage defects during deposition while maintaining ease of manufacture through standardized layer formation processes in the display area.
Data Source
AI summary
A display device includes: a first conductive layer including a gate electrode on an active layer in a display area and a first pad electrode on the substrate in a pad area; a second conductive layer on the first conductive layer in the display area and connected to the active layer; a third conductive layer on the second conductive layer in the display area and including a first connection electrode; a fourth conductive layer on the third conductive layer in the display area and including a second connection electrode connected to the first connection electrode; a light emitting element on the fourth conductive layer in the display area and connected to the second connection electrode; and an upper touch layer including an upper touch electrode on the light emitting element in the display area and a second pad electrode electrically connected to the first pad electrode in the pad area.